In recent years, it has become very common to use wind for the generation of electrical power. In order to do this, wind is captured by a set of blades of a wind power plant. The captured wind causes a shaft connected to the set of blades to rotate. The shaft is typically connected to a rotor of an electrical generator which is rotated in accordance with the rotation of the shaft, possibly at a multiple of the rotation speed of the shaft in case the rotor is connected to the shaft via a gearbox. The electrical generator converts the mechanical power provided by the wind in form of the rotation into electrical power which may be supplied to a power grid.
The electromagnetic power of, e.g., a synchronous electrical generator depends on the magnitude of the stator flux vector and its location with respect to the rotor flux vector. If the position of the rotor flux vector is known, it is possible to control the stator flux such that a desired magnitude of the electromagnetic power provided by the electrical generator is achieved.
However, if an error occurs in the stator flux control and the stator flux is not controlled correctly, e.g., due to an error in the calculation of the respective control signal or due to malfunction of a sensor in the measurement of an input parameter to the stator flux control scheme, the stator flux control may fail and the electrical and electronic devices of the system, e.g., the wind turbine generator converter control system, may be damaged.
Hence, an objective of the present invention may be seen in providing a control method for an electrical generator which allows reducing the risk of a failure of the stator flux control system compared to known methods.
Another objective of the present invention may be seen in providing a control method for synchronizing the converter output voltage with the generator Bemf (back electromotive force) voltage before connecting the generator with the converter so that the inrush current and torque in power connection transient is minimized. This may reduce the stress on power devices and the driver train.